Not looking to beat a dead horse here, as it sounds like drabina has had all questions responded to with good advice, so I'm just throwing in my two cents:
I run a stock `68 L72 427 in my Z24 Impala with 11:1 compression. The car has ~43k original miles on it, and the last thing I would ever want to do is damage or destroy this engine as it is original to the car. I don't disagree with anyone else's advice here, so this is just an FYI to give you some additional perspective on what's worked best for me over the years. My car probably see's about 500-600 miles per year.
> I have been using Mobil-1 10W-30 Synthetic oil for about 5 years with no leak issues whatsoever. I ran Penzoil organic 10W-30 prior to that. The Synthetic oil is probably more for my own piece of mind more than anything else, as I can't honestly say that I've noticed any significant performance difference. I just believe it provides superior wear protection, and is worth the extra cost.
> This is a solid lifter engine w/o hardened valve seats. I do add ZDDPlus with every oil change (about every 1000 miles, or once a year). I buy this through Dennis Kirban:
> While it may not be practical (or necessary) for you to use a lead additive for a daily driven `70 350 small block, but with 10.25:1 compression I would think you would at least want to use a 92 octane premium pump gas for the best performance. I use Chevron 92 as a starting point with every fill-up, then add 4 qts. of Octanne Supreme 130 with real TEL, 12 ounces of Chevron Octane Booster, and a couple of pints of Stabil (just because the car sometimes sits for extended periods between being driven). This puts the octane level in my 24 gallon tank up to about 112. Any lower than this with the L72, and I will experience detonation issues. Octane 130 Supreme can only be purchased on-line, and I buy it here through Battery-Stuff.com:
Yes, this all gets expensive, but again, is worth while in my opinion to keep a higher compression engine running as it should. Remember, back in the late 60's/early `70's, Lead and 112 octane fuel was pump gas, and ZDDP was in your oil. This is what these engines were desinged to run on.
I believe in being as "green
" as anyone else and as I mention, I limit the use of my collector cars to summer time cruise-in's and shows.
Hope the information helps.